Understanding plant structure is important to human survival. Plants can live without humans, but humans cannot live without plants. In other words, plants are producers in the food chain, and humans are consumers. Over time, humans have used their understanding of plant systems to develop many ways to cultivate plants for food.

Plants have two major structural systems: the root system and the shoot system. Each of these structural systems has specific roles in the function and health of the plant. The root system brings in water and nutrients from the soil, grounding the plant in the same way our feet help us balance. The shoot system transports water and nutrients to leaves and flowers. The leaves of the plant are the main location for photosynthesis. Plant reproduction occurs through pollination of the flower and fertilization.

An analysis of plant structure leads to many questions: How do plants and animals differ? What parts of plants do we eat? Why do plants continue to grow throughout their lives? How do plants make their own food? How do plants reproduce? Are there male and female plants? What is the structure of plant cells? How are they similar to and different from the cells in the bodies of animals?

The question “How do plants make their own food?” leads to a study of photosynthesis, one of nature’s most powerful processes and the key to understanding why plants are so essential to our lives.

Not only are plants the producers that support all food chains and webs, they also contribute to the air we breathe. The word photosynthesis comes from the Greek “photo” meaning light and from “synthesis” meaning putting together. So “photosynthesis” is the process by which plants make their own food or energy using the light of the sun.

Photosynthesis takes place within chloroplasts, which are organelles or specialized parts of plant cells that absorb sunlight. Chloroplasts contain chlorophyll, the pigment that makes plants green and that conducts the work of photosynthesis.

Carbon dioxide (CO₂) is present in our atmosphere and is exhaled by humans and other animals. Water (H₂O) comes from precipitation. In photosynthesis, carbon dioxide and water combine with light to produce a carbohydrate called glucose (C₆H₁₂O₆) that provides energy or food for the plant. In addition to creating glucose, photosynthesis also releases oxygen (O₂) into the atmosphere for animals to breathe.

The following formula describes the process of photosynthesis:

6 CO₂ + 6 H₂O + Light → C₆H₁₂O₆ + 6 O₂

When we get the energy needed for growth, health, and survival by eating fruits and vegetables, we too are depending on the carbohydrates produced through photosynthesis, just like the plants themselves.

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